Throttle body upgrade to non fly by wire

[kmack46]

Hi guys some one told me that the program Wheeler dealers showed a XK8 having its fly by wire throttle body upgraded by fitting a unit that was a non fly by unit does any one have any I formationon on this? My lady is a 1996 XK8
Thanks guys
Ken

[Astromorg]

As I recall he only replaced a faulty Throttle Body with a replacement of the same type. The integration of the TB in the Engine Control System is such that a change to another type - especially non fly-by-wire - would not be very easy.

[kmack46]

Hello
Thanks for the reply l saw that maybe Weber ca bs could be fitted

Ken

[mike020150]

Hi Ken,
Just seen this posting and I'm wondering why you want to make your car go slower and use more fuel. It seems counter-intuitive! Mike.

[Astromorg]

Although the 4.0 litre engine did not have a total fly-by-wire throttle, it would be wrong to think that it was plain mechanical and therefore possibly easily replaced with a carb arrangement. Jaguar describe it this way:

The throttle body assembly has the following features:
Convential cable operated input shaft connected to the accelerator pedal.
Mechanical guard to limit throttle angle should driver demand exceed ECM controlled parameters and a mechanical back-up in the event of a throttle motor failure.
Vacuum actuator for operation of the mechanical guard in cruise control mode.
Throttle valve (blade) to regulate air flow into the engine.
Thermostatic air valve to allow and control air by-pass around the throttle.
DC electric motor to operate the throttle in response to ECM control.
Three sensors (accelerator pedal, mechanical guard and the throttle valve) to relay positional information about the input shaft to the ECM.
Return and control springs fitted to the input shaft, mechanical guard, throttle valve and dc motor drive gear.

There are seven throttle control modes:
NormalCruise, Mechanical guard, Fixed idle, Redundancy, Full authority, Engine shut-down.

Normal mode occurs when the ECM uses the mechanical and monitoring arrangement of the throttle valve to control throttle opening. The ECM does not permit driver demand to be exceeded but it can be restricted to allow for such features as stability / traction control, or engine power limitation.The ECM determines engine idle speed by controlling the throttle valve motor to vary the blade angle between the non-adjustable preset limits of the mechanical guard and the throttle valve motor.Cruise mode is engaged as a result of the ECM calculating and controlling the required throttle valve opening via the vacuum system. When the driver releases the throttle pedal, the input shaft disengages from the mechanical guard or the vacuum actuator pulls the guard away from the throttle valve. The throttle pedal will feel light should it be pushed again to accelerate (pressing the pedal further will re-engage the input shaft with the mechanical guard and restore normal feel).

Obviously, all that lot could just be removed or disconnected, but then the ECU is going to get upset and throw a wobble. OK, you could get a custom ECU suitably programmed, because one is still needed to sort the ignition system, the variable valve timing and the gearbox, though with Webers you're probably thinking of a manual gearbox and all that involves! There's lots of other aspects to consider, not least of which might be the emissions test at MoT time.

All I'm trying to do is point out the magnitude of this idea. Take a lot of informed technical advice (more than I can offer!!) before committing!!

[kmack46]

Hello Astromorg
Thank you for your post l have read it and l can see it basically would cost a fortune to go down the road l had in mind. I just want to solve a small problem my car has had for some time now. I have replaced the throttle body spark plugs ignition coils and replaced the intake manifold with a new one and all it’s gaskets. The car runs great once it’s up to temperature but before it does it runs slightly rough l have replaced the temp sensor to and checked all the vacuum pipes and can’t get to the bottom of it. I am thinking now that it could be the oxygen sensors as some times l can smell petroleum as it runs lean. I have a official Jaguar test kit with all its probes l bought some time ago and l would be only too happy to give it to a good home if some one agreed to carry out my tests if and when needed

[Astromorg]

Buying new O2 sensors on a hunch could prove an expensive choice!

The smell of petrol is not good, but interesting because it could be (probably is) a leak. Depending where and what sort of leak it might be, it could give rise to the intermittent lean running during warm-up.
Maybe get sniffing!

[deuce2000]

the English company https://www.pinkbatmotorsports.com/ is building one new TB for 4.2L supercharger versions with electrical connections.

diameter: 83mm

ready soon..